Contact force monitoring technology during cardiac catheter ablation has become a major issue as both appropriate RF delivery and risk-free therapy have been more and more significant. In this study, an elastic waveguide was utilized to detect the contact force of 0 to 40 gF applied at the end of the sensor tip. The sensor showed a hysteresis between the force loading and releasing because of the elasticity of waveguide. The sensing responses were nearly linear and the sensitivity was about 0.2 mV/gF.